The present disclosure relates generally to signal transmission in communication systems.
In communication systems, a Carrier Phase Recovery System (CPRS) may be used to estimate and compensate for frequency and phase differences between a carrier frequency of a received signal and a local oscillator frequency of the receiver for non-coherent demodulation. In addition, the CPRS is used to remove phase noise contributions from both the transmitter and the receiver clocks. In an ideal communications system, the carrier frequency and phase of the transmitter and receiver would be perfectly matched, thereby permitting optimum demodulation of the modulated baseband signal.
Obtaining signal lock between the receivers and transmitters can prove to be challenging because the oscillator frequency of the transmitters and receivers are rarely identical as the receivers are usually independent of the transmitters. Each transmitter and receiver has an oscillator with unique frequency and phase characteristics, including phase noise degradation that may be introduced by an oscillator. As a result of this less than ideal relationship between the receivers and transmitters, a number of frequency and phase variations must be estimated using information in the received signals to receive the original transmitted signal and produce acceptable performance.
Optimum selection of the Carrier Phase Recovery Loop (CPRL) bandwidth, B, is especially important in low data rate applications and can significantly impact performance. The choice of CPRL bandwidth impacts performance in the presence of phase noise. This is because narrow loop bandwidth inhibits phase noise tracking, and wide loop bandwidths are more susceptible to thermal noise. Therefore, it is necessary to determine an optimum CPRL bandwidth in order to achieve optimum low data rate performance